The mechanisms of senescence in cells is likely a universal phenomenon, and much research has focussed on the role ofReactive Oxygen Species (ROS). The ovary is a prime site for ROS production, and it is possible that inappropriate production of reactive oxygen species in the ovary, or reduced antioxidant status leads to pathophysiology, such as infertility. Infertility in women is an increasing clinical problem. The demographics of western living has produced a greater number of women who postpone attempts of child-bearing to their late thirties, and this has corresponded with an increase in female infertility. Although infertility is multi-factorial, its cause in the population of aging women is mostly due to oocyte senescence, highlighted by the success of pregnancy rates in in vitro fertilization programs when older women receive oocytes donated from younger women. Meiotic competence of in vitro matured human oocytes from reproductively aged ovaries is impaired, and there is an increased occurrence of aneuploidy in aging oocytes that may be the result of effects of ROS on spindle formation. In vitro maturation of germinal vesicle stage mouse oocytes under conditions that increase oxidative stress induces chromosomal anomalies. Vitamin C has been considered the preeminent antioxidant in the ovary. Guinea pigs that are vitamin C deficient are anovulatory and have marked degeneration of follicles, failure of implantation, and an increased rate of spontaneous abortion. Ascorbic acid deficiency also results in premature resumption of meiosis in the oocyte with subsequent oocyte destruction, while antioxidants prevent this phenomenon. In addition, mice fed a diet supplemented with vitamin C and vitamin E have a reduced frequency of abnormal ovulated oocytes, including reduced occurence of aneuploidy and diploidy compared to animals fed an unsupplemented diet. Regulation of follicular levels of vitamin C is likely to be important in protecting the oocyte from the effects of ROS. Furthermore, since ROS formation is associated with apoptosis and oocyte senescence, the vitamin status of the follicle and oocyte will predict the developmental potential of the oocyte. Preliminary trials with the self-referencing ascorbic acid probe are exploring its use to determine regulation of ascorbic acid by an individual follicle, oocyte cumulus cell mass or single oocyte. In vitro maturation of follicles under varying culture conditions of oxidant stress will be studied and correlated with ascorbic acid regulation, and in vitro fertilization rates and early embryo formation. Since oocyte senescence may be the result of reduced antioxidant tone of follicles in older animals, the effect of age on regulation of follicular transport of ascorbic acid will be assessed.